1. Field of the Invention
This invention relates to aqueous liquid treatment compositions suitable for forming on metal surfaces, particularly ferriferous metal surfaces, a novel coating containing a mixture of iron phosphate(s) and a boron containing lubrication promoting material. These coatings, either as applied or preferably after the application of additional lubricant materials that are already known in the art, are protective against mechanical damage during cold working of the underlying metal. Processes for using these compositions are also part of the invention.
2. Statement of Related Art
A very widely accepted currently conventional method of preparing metal surfaces for cold working is to apply a heavy zinc phosphate coating to the surface and then apply a composition containing an alkali metal soap, usually sodium stearate, which reacts with the zinc content of the zinc phosphate coating to form a very effective lubricant layer that is believed to contain zinc soap. This practice produces excellent results, but current environmental concerns militate against the use of zinc and other heavy metals such as nickel, manganese, and calcium, which are often required to obtain the best lubricant properties when using this technique. The metal soap containing coatings formed on metal surfaces in this way are also sources of a substantial dust nuisance in many cases.
Decades ago, iron phosphating was commonly used as a basis for lubricant layers for cold working metals, but the thicker layers provided by zinc phosphating generally have been found to produce more effective lubrication and thus are highly preferred. Conventional aqueous iron phosphating treatment compositions contain primarily alkali metal or ammonium phosphates, sometimes additional phosphoric acid, and usually some kind of accelerator as their active ingredients.